To troubleshoot a Compute Engine image that is not booting up, what action should be taken?

Checking Compute Engine OS logs using the serial port is an essential step when troubleshooting a virtual machine that is not booting up. The serial port provides valuable output during the boot process, including any error messages or warnings that the operating system encounters. By accessing these logs, you can pinpoint the issues preventing the virtual machine from completing its startup sequence. This targeted approach allows you to identify the root cause more effectively, whether it's a configuration problem, a missing dependency, or a startup script failure.

Utilizing the serial port for logging is particularly advantageous in scenarios where the graphical console is unavailable or unresponsive. It facilitates deeper insights into the boot process, thereby enabling quicker resolutions. This method is a standard practice in cloud environments where diagnostics are crucial for maintaining uptime and reliability.

In contrast, exporting the disk for boot logs may not yield immediate insights into the boot failure, as it involves additional steps that could delay troubleshooting. Similarly, creating a new feature branch or installing Packer locally does not directly address the immediate issue with the non-booting image; those actions are more relevant to the image-building process rather than troubleshooting an existing instance.